add mainline kernel mirror support

[amazingfate]

Description

Mainline mirror is not supported since armbian-next. Current code support google, tuna and bfsu as mainline kernel source: https://github.com/armbian/build/blob/main/lib/functions/configuration/main-config.sh#L170-L187. We have to use kernel source from git.kernel.org to support curl.

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Please also note any relevant details for your test configuration.

• Build with MAINLINE_MIRROR=tuna

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• Any dependent changes have been merged and published in downstream modules

[hzyitc]

Not a good idea.

It will get wrong data when sync in progress.

[amazingfate]

Not a good idea.

It will get wrong data when sync in progress.

We use mirror for fast speed, not for up-to-date data.

[amazingfate]

We will first get commit sha1 from mirror source, and then download the Makefile from git.kernel.org:

--> (2) INFO: Producing new & caching [ GIT_INFO_KERNEL ]

--> (2) INFO: Fetching SHA1 of 'branch' 'refs/heads/linux-6.4.y' [ https://mirrors.tuna.tsinghua.edu.cn/git/linux-stable.git ]

--> (2) INFO: SHA1 of branch refs/heads/linux-6.4.y [ 'eb3cdb587879a7794c7f649011c565d7a94f3e2e' ]

--> (2) DEBUG: Fetching Makefile body [ linux-6.4.y ]

--> (2) DEBUG: Fetching Makefile via HTTP [ https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/plain/Makefile?h=eb3cdb587879a7794c7f649011c565d7a94f3e2e ]

--> (6) DEBUG: Fetched Makefile from URL [ https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/plain/Makefile?h=eb3cdb587879a7794c7f649011c565d7a94f3e2e ]

So we will always get correct data @hzyitc

[rpardini]

Well -- if the mirror is lagging behind, the SHA1 returned will be old, but will still exist on git.kernel.org, and although there is a chance you'll get an older version, it will work.
The alternative would be to do the main SHA1 lookup on kernel.org, then try to use the mirror, which would not have that SHA1 and fail.